Tiltable x-ray examination table

ABSTRACT

A tiltable patient table having a carriage that is displaced by means of a drive system; the table has a safety device whereby the carriage is connected to a drawing means such that a measurable force occurs whenever the carriage collides with another object, such as the patient, and automatic controls are affectuated.

' United StatesPatent I [191 Schmedemann TILTABLE X-RAY EXAMINATION TABLE [75] Inventor: Walter Schmedemann, Hamburg,

Germany [73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: Dec. 21, 1972 [21] Appl. No.: 317,410

[30] Foreign Application Priority Data Jan. 8, I972 Germany 2200848 52 us. cig. .269/323, 250/444 51 int. Cl A6lg 13/00 58 Field of Search 250/444, 445, 446, 447,

[56] References Cited UNITED STATES PATENTS I 3,473,024

l0/l969 Feiertag 269/323 X 11] 3,822,875 [451 July 9,1974

3,493,745 2/1970 Patser 250/277 FOREIGN PATENTS OR APPLICATIONS 197,994 5/1938 Switzerland 269/322 Primary Examiner-Granville Y. Custer, Jr. Assistant ExaminerMark S. Bicks Attorney, Agent, or Firm-Frank R. Trifari [5 7] ABSTRACT A tiltable patient table having a carriage that is displaced by means of a drive system; the table has a safety device whereby the carriage is connected to a drawing means such that a measurable force occurs whenever the carriage collides with another object, such as the patient, and automatic controls are affectuated.

6 Claims, 5 Drawing Figures l TILTABLE X-RAY EXAMINATION TABLE BACKGROUND OF THE INVENTION The invention relates to a safety device for an X-ray examination apparatus, comprising a tiltable patient table with a drive system for displacement of a carriage on the patient table, said carriage being connected to a drawing means via fixing means said patient table also comprises a member for measuring the table tilt.

Swiss Pat. No. 197,996 describes an X-ray apparatus which comprises a tiltable holder for the X-ray tube where the motorized displacement of the X-ray tube with respect to the holder can be effected in accordance with a pressure exerted on a grip and also in accordance with the relevant tilt of the holder. The direction in which the X-ray tube is to be displaced with respect to the holder is indicated by the grip, while the torque required for this displacement is obtained via a variable resistor and also via resistors which can be connected and disconnected. Consequently, an increased pressure onthe grip in the one or the other direction has no effect on the speed of the displacement of the X-ray tube with respect to the holder. Even if the X-ray tube inadvertedly runs against or is pushed against an object, there is no effect on the drive system. The X-ray tube thus cannot be inadvertedly pushed againsta patient at a large force. In this context, of course, X-ray tube is to be understood to mean the parts enveloping the X-ray tube.

Austrian Pat. No. 209,449 describes a'spring-mass balance for an X-ray examination apparatus; also, in this device a weight is shifted and a carriage with associated parts is displaced along a patient table. Various driving forces must then be applied for displacing this carriage in accordance with the tilt of the patient table with respect to the vertical. In this known device these forces must be balanced by a spring-mass balancer. Also this arrangement does not comprise any additional safety provisions against displacement, for example, when the carriage is bumped or collides with a patient on the patient table.

' German Pat. No. 1,900,727 describes an X-ray examination apparatus having a limit-position adjusting .circuit. Therein, for example, the momentary position of the cursor ofa potentiometer, incorporated in an appropriate circuit arrangement, is an exact measure for the relevant position of the .apparatus component. On the basis of the circuit arrangement shown, a given end position or also a position of the potentiometer cursor can be arbitrarilyused for switching off a switch. However, this has nothing in common with a so-termed safety device as will be explained hereinafter.

During displacement of a carriage on the patient table, it is common practice in known arrangements to produce a displacement of the carriage on the patient table in the relevant direction by exerting a pressure on a grip. The displacement will be effected at an acceleration or speed which is higher when the pressure exerted on this grip is higher. The patient table is also provided with devices for detecting tilting of the table with respect to the vertical.

As long as the-displacement of the carriage on the patient table is normal, the progress in the desired direction will be at the desired acceleration or speed. However a collision with the patient, for example, had to be anticipated thus far by the examining physician and the apparatus componenthad to be decelerated in time.

J2 SUMMARY OF THE New INVENTION The invention has for its object to provide a safety device which, for example, in the case of even the slightest collision, is immediately and automatically actuated, blocking the displacement of the carriage on the patient table abruptly. This alone, however, is not yet sufficient because if the operation of the safety device is to be reliable, not only the drive but also the actuation of the components of the safety device is performed in a differentiated manner in accordance with the tilt of the patient table.

This object is achieved in a safety device of the, kind set forth according to the invention in that the fixing means are constructed such that any force to which they are exposed which exceeds a pre-set value, produces a signal which switches off the driveunit in accordance with the tilt of the table. The fixing means consist of two helical springs whose outer ends are connected to the carriage and whose ends which face each other are connected together to a drawing chain, and also to a cursor of a potentiometer.

In a further embodiment according to the inventio at least one drive motor is suspended. to be tiltable about its axis from appropriately constructed springs, means being provided for measuring the tilt, the said means being connected to the cursor of a potentiometer. The drive system can consist of a drive motor and a guide roller which are joumalled to be resilient in the longitudinal direction of the patient table, the connecting rod system comprising at least one switching cam, the switching contacts being arranged in a housing which is displaced in accordance with the tilt of the patient table.

The circuit arrangement can alternatively comprise two potentiometers in bridge-connection, one potentiometer being the force-measuring potentiometer and the other potentiometer being the position potentiometer, the cursors of these potentiometers being connected to a common analyzing circuit. The forcemeasuring potentiometer can be connected to one branch of the bridge via at least one adjustable compensating potentiometer which is adjusted by the manual force exerted on the grip. One embodiment according to the invention is shown in the drawing and will be described in detail hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 shows a detail of the circuit arrangement according to the invention, I

FIG. 4 shows a circuit arrangement which is similar to that shown in FIG. 3 but elaborated somewhat and FIG. 5 shows a further embodiment of a safety device connected to a patient table similar to that'of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 the reference numeral 1 denotes a patient table on which a drive motor 4 and a guide roller 5 with a drawing means in the form of a chain 6 are arranged via bearing blocks 2 and 3. The patient table 1 can be tilted about a pivot 7 and can be secured to the floor 9 via a bearing block 8. A diagrammatically shown potentiometer 10 (position potentiometer) has a cursor 11 which will be displaced on the potentiometer 10 when the patient table 1 is tilted about the pivot 7.

The reference numeral 12 denotes a carriage to which, for example, the X-ray tube with the control unit are connected. This carriage 12 comprises a grip 13 which can be displaced over a small distance in the directions denoted by the arrows 14. This grip acts, for example, via a well known corresponding lever system not shown in the figure, on a resistor 15 which is connected in an appropriate circuit arrangement, diagrammatically shown. So, the connection points do not have the same meaning as in a circuit diagram.

As is shown with guides 16 and 17, the chain 6 passes freely through the carriage l2, and the carriage 12 is connected to the chain 6 only at the position 18 via two helical spring parts 19 and 20. A cursor 21 of a potentiometer 22 is connected to the junction of the two helical spring parts 19 and 20 (force-measuring potentiometer).

As long as the carriage 12 is normally moved downwards and upwards in the table position shown, the cursor 21, remains in the same position on the potentiometer 22. Only if a collision causes an inadmissible shock the springs 19 and 20 are compressed or expanded in accordance with the direction of the collision, with the result that theposition of the cursor 21 on the potentiometer 22 changes.

When the apparatus is tilted, however, the position of the cursor 11 on the potentiometer 10 changes, for example, as denoted by the broken line 11' in FIG. 1. However, the position of the cursor 21 on the potentiometer 22' also has been changed. The safety device is actuated whenever the cursor 11 or 21 of a potentiometer 10 or 22 departs from the predetermined position with respect to the other cursor.

This is shown in principle, by way of example, in a circuit arrangement in FIG. 3. Both potentiometers 10 and 22 can be connected in forming a wheatstone bridge, and at point 24 an output signal is obtained, via an appropriately connected operational amplifier 23 (analyzing circuit), if the equilibrium of the bridge is disturbed.

FIG. 4 shows an elaboration of the circuit arrangement shown in FIG. 3, the only difference is that the resistor 22 comprises two additional resistors 25 and 26 having tappings 27 and 28 (compensation potentiometers) which can be mechanically connected to each other, as indicated with lines 29 and also to the manually-operated grip 13. The apparent interference signal on the potentiometer 22 which is caused by the acceleration of the components mounted on the carriage 12, resulting from the mass inertia and the acceleration force, is thus compensated for, while the signal on the resistors 25 and 26 is proportional to the manual force exerted on the grip 13 and hence also to the acceleration force of the drive motor 4. When these signals have opposite directions, they cancel each other. It is thus possible to choose the critical switch-off force of the system to be smaller than the largest possible acceleration force of the drive system. The resistor 10 with the tapping 11 can be constructed as a sine potentiometer, i.e. the resistance adjusted by the tapping l1 corresponds to the sine of the tilt.

5 journal the drive motor, as shown in FIG. 2, in a freely suspended and tiltable manner at point 30, while making use of a housing having a tilting plate 31. The latter has a pin 32 which is again arranged between two helical springs 33 and 34. In this manner the torque of the motor or the fluctuations of the drive system act on the potentiometer tapping 21 of the resistor 22, the latter component, of course, being connected to the patient table 1.

FIG. 5 shows a further embodiment of the safety device according to the invention. In this case the drive motor 4 and the guide roller 5 with the chain 6 are journalled in bearings 35 and 36 in a rod system 37. Both ends of the rod system 37 project through corresponding cut-outs 38 and 39 in corresponding projections on the patient table 1, and the system is held in position, for example, via helical springs 40 and 41. A projection 42 actuates contacts 43 in the case of fluctuations of the drive. The contacts are displaceable with respect to the projection 42, via a connecting system consisting of levers 44 and 45, in accordance with the tilt of the patient table 1 with respect to the vertical. If the patient table 1 is tilted, the direction and the extent of the shifting of the lever 44 corresponds to the direction and the extent of the shifting of the rod system 37. This is a result of the tilt-depending point of application of the force of gravity and the resulting yielding of the springs 40 and 41. An interference force acting on the carriage 12 has via the drawing means 6 and the drive motor 4 a comparatively shifting effect of the rod system 37 and thus switches the contacts 43.

I claim:

1. In an x-ray examination apparatus including a base, a tiltable patient-table carried by the base, a carriage displaceable on said table, and drive means for displacing the carriage, the improvement in combination therewith of a safety device for quickly stopping the drive means from further displacing said carriage when said carriage collides with an object, comprising first means for sensing the amount of tilt of the table and for providing a corresponding signal, second means for sensing the impact and deceleration of the carriage at the time of said collision and providing a corresponding signal, actuator means responding to signals from said first and second means for directing said drive means to cease displacing said carriage, when either of said first and second means produces a signal that departs from a predetermined value relative to the other signal. I

2. Apparatus according to claim 1 operable with a source of electrical current, wherein said drive means includes an electric motor and circuit means for conducting current from said source to said motor, said first means comprising a first potentiometer and cursor, and tilting of said table causes movement of said first cursor, said second means comprises a second potentiometer and cursor, and helical spring means having its ends secured to said carriage and an intermediate part between said ends secured to said drive means and to said second cursor, whereby a collision and deceleration of said carriage produces corresponding movement of said second cursor, said apparatus further comprising circuit means which includes said first and second potentiometers and their cursors, and third means for analyzing said signals from said first and second means and providing a resultant signal, said actuator means being responsive to said resultant signal for controlling said drive means.

3. Apparatus according to claim 1 wherein said first means comprises a force-measuring potentiometer for measuring force resulting from said collision, said second means comprises a position-measuring potentiometer for measuring the amount of tilt of said table.

4. Apparatus according to claim 3 wherein said actuator means comprises a wheatstone bridge circuit in circuit with said force-measuring potentiometer.

$2223 v UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION July 9, 1974 Patent No. 3'822'875 Dated l -(x) WALTER SCHMEDEMANN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the title, *after "Foreign Application Priotity Data Jan. 8, 1972 Germany" delete "2200848"and insert -'P-.2200848.6-

Signed and sealed this 8th day of October 1974.

(SEAL). Attest:

he McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. In an x-ray examination apparatus including a base, a tiltable patient-table carried by the base, a carriage displaceable on said table, and drive means for displacing the carriage, the improvement in combination therewith of a safety device for quickly stopping the drive means from further displacing said carriage when said carriage collides with an object, comprising first means for sensing the amount of tilt of the table and for providing a corresponding signal, second means for sensing the impact and deceleration of the carriage at the time of said collision and providing a corresponding signal, actuator means responding to signals from said first and second means for directing said drive means to cease displacing said carriage, when either of said first and second means produces a signal that departs from a predetermined value relative to the other signal.
 2. Apparatus according to claim 1 operable with a source of electrical current, wherein said drive means includes an electric motor and circuit means for conducting current from said source to said motor, said first means comprising a first potentiometer and cursor, and tilting of said table causes movement of said first cursor, said second means comprises a second potentiometer and cursor, and helical spring means having its ends secured to said carriage and an intermediate part between said ends secured to said drive means and to said second cursor, whereby a collision and deceleration of said carriage produces corresponding movement of said second cursor, said apparatus further comprising circuit means which includes said first and second potentiometers and their cursors, and third means for analyzing said signals from said first and second means and providing a resultant signal, said actuator means being responsive to said resultant signal for controlling said drive means.
 3. Apparatus according to claim 1 wherein said first means comprises a force-measuring potentiometer for measuring force resulting from said collision, said second means comprises a position-measuring potentiometer for measuring the amount of tilt of said table.
 4. Apparatus according to claim 3 wherein said actuator means comprises a wheatstone bridge circuit which includes as branches thereof, said potentiometers of said first and second means.
 5. Apparatus according to claim 2 further comprising a compressible grip operable with said drive means, wherein speed of displacement of the carriage corresponds to compressive force applied to said grip.
 6. Apparatus according to claim 5 further comprising at least one adjustable compensating potentiometer which is varied by the force applied to said grip, and is in circuit with said force-measuring potentiometer. 